浮游式黑潮發電渦輪機在波浪作用下的動態反應模擬

波浪為海洋工程領域中一項重要的環境外力因素，當氣候不佳或是颱風來襲時，更大的波浪也會隨之產生，此時於水下運轉中的黑潮發電渦輪機組在受到波浪強制力作用下，會造成機組運動狀態的改變，而導致發電性能下降，甚至可能造成機組構件受損等問題。本研究主要利用OrcaFlex軟體來模擬浮游式黑潮發電渦輪機組(Floating Kuroshio Turbine；FKT)，在受到波浪作用下，機組的動態反應及性能影響評估。　　本研究利用OrcaFlex軟體來建置模擬FKT機組之環境流場，在工作水深25m中加入不同波長之波浪外力，並配合不同波高波長比，探討在正常工作水深下，不同大小之波浪及波高對機組造成的運動狀態影響。另外，針對淺水深10m以及避長浪水深40m，分別加入不同波長之波浪外力，探討機組在遭遇長浪時於不同水深的影響程度。由於當FKT機組受波浪作用下，轉子轉速會產生明顯震盪，本模擬研究考慮轉子制動方式，使轉子最大轉速受制在額定轉速內運轉。　　本研究結果顯示，當FKT機組在受到波浪作用下，機組運動狀態會有明顯的改變，包含垂向、軸向的位移以及縱搖變化等，此情況會導致連接機組的纜繩不斷拉扯、降低FKT機組發電效率等問題產生，尤其在淺水深10m時更加嚴重。而機組於避長浪水深40m時，上述情況則有明顯的改善。未來當機組在實海域運轉時，必須注意機組因波浪作用造成反覆的震盪，除了發電效能下降之外，長期可能導致機組構件及纜繩因不斷拉扯導致的疲勞破壞等問題產生。

關鍵字

洋流；浮游式黑潮發電渦輪機組； OrcaFlex ；波浪；動態反應

並列摘要

In bad weather like typhoon, waves are always considered as a key environmental factor in ocean engineering. In this condition, motions of Floating Kuroshio Turbine (FKT) could be induced by wave exciting forces, and some problems may be caused, such as the performance of power generation reduced and even damaged. In the present study, simulation software OrcaFlex is applied to simulate the dynamic responses and performance variation of the Floating Kuroshio Turbine under the action of waves. 　　This study builds an environmental flow field for FKT simulation in OrcaFlex, considering waves of different wavelengths and wave height ratio acting on the FKT located at 25m under water surface (normal operation depth) to investigate the influence of waves to the FKT. Furthermore, by adding the wave exciting forces of different wavelengths to the FKT located at 10m under water surface (shallow depth) and 40m under water surface (deeply submerged condition for avoiding long waves), the wave effects to the FKT depending on its submerged depth are investigated. Since FKT rotor could suffer significant oscillations under the wave effects, this study revised the torque performance of the generator so that the maximum speed of the rotor can be kept without over the rated speed too much. 　　According to the simulation results, FKT dynamics including vertical and longitudinal motions, pitch motions may become significant and then not only the performance of power generation will be reduced, but also tension variation of mooring line will be caused. This phenomenon is even significant at submerged depth of 10m, but it can be improved at submerged depth of 40m. In the future, when the FKT operates in real sea, the issue like cable fatigue damage caused by long waves should be also concerned.